ML20090M536

Package Consisting of Util Responses to AEC Questions on Facility High Energy Line Breaks Outside of Containment

ML20090M536
Person / Time
Site:	Monticello
Issue date:	03/21/1974
From:	NORTHERN STATES POWER CO.
To:
References
NUDOCS 9105060229
Download: ML20090M536 (17)

Text

-

AEC DI

'IBUTION FOR PART 50 DOCKET MA7 TAL (TLMPORARY FORM)

CONTROL N0t 2135 FILE:Mid C FROM:

DATE OF DOC DAE REC'D LTR MEMO RPT OTHER Northern States Power Co.

Minneapolis, Minnesota 55401 NONE 3-20-74 e

A. V. Dienhart ORIC CC OTHER SENT AEC PDR X

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0 ORIG TO:

SENT LOCAL PDR X

CLASS UNCLASS PROP u 7s INPUT NO CYS REC'D DOCKET NO:

0 50-263 XXXXx 1

4 ENCLOSURES:

DESCRIPTIC'...

No Ltr of trans ree'd.......

Response to AEC Questions on Menticello High Energy Line Breaks Outside of Contain-ACKNOWLEDGED l>0NUf REMOVE PLANT NAME: Monticello

( 40 cys rec'd )

l FOR ACTION /INFORMATION 3-21-74 GC BUT12R(L)

SCHRENCER(L) 44tIDiANN(L)

REGAN(E)

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VREG FILE TECH REVIEW DENTON A/T IND LIC ASST BRAIIMAN

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UBE w/ nput MOORE (L)(BWR)

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DEYOUNG(L)(PWR)

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INFO V$KOVHOLT (L)

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B. XING DENISE IPPOLITO YOUNGBLOOD WADE (E) vvARGA REG OPR VtEDESCO REGAN WILLIAMS (E)

Vli1ECKER FILE & REGION (3) vt0NG PROJECT LDR WILSON (L) vt:ARTEE S. REED (L)

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hSIC(BUCHANAN) 1-ASLBP(E/W Bldg.Rm 529) 1-GERALD LELLOUCHE V1*-

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Cetu:nt:n hi efh 5 Responses TO AeC QUESTIONS ON MONTICELLO HIGH ENERGY l

LINE BREAKS OUTSIDE OF CONTAINME NT i

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1.

QUESTION:

Provide the design pressure of the following; 1

a.

Condenser Compartment (pa ge 16) i 1

b.

HFCI Compartment (page 24)

I R WCU Pump and lleat Exchanger R oom (pa ge 28) c.

I d.

Main Steam Chase i

1 A NSWER :

The maximum allowable pressures are as follows:

5 COM PA R TME N T MAX. A LLOWA BLE PEAK PRESSURE i

PR ESSUR E (PSID)

(PSIG)

C ondense r

8. 4

1. 4 HPCI

2. Oc

0. 9 RWCU Pump 16.0

0. 2 i

RWCU Heat Exchanger 16.0

0. 6 Main Steam Chase 13.4 12.2 Original design pressure from tornado requirements.

4 l

In the study we utilized Theory of Plates and Shells, McGraw-Hill 2nd Edition, 1959 by Timoshenko and Weinowsky-Krieger to determine the maximum allowable pressures for each c ompa r tme n t.

The condenser compartment maximum allowable pressure in based on a solid wall.

A c tually, the condenser compartment has one section made from concrete blocks.

The maximum pressure for the concrete block wall is difficult to determine but even if the concrete blocks fail, no safeguard equipment is located in their path.

If the concrete block section fails 4

_l.

i

+ - - -

. - _ - - _ = - -

1 I

t at a low e r pressure than 1. 4 psi, the compartment peak j

pressure would be reduced due to the added vent area.

Therefore, this damage to the condenser compartment will not prevent the safe shutdown of the pla n t.

I l

In all cases, the maximum allowabic compartment pressures were either below the original design pressures or within

]

the maximum allowable pressure calculated from Timoshenko and Weinowsky-Krieger, as noted in the above tabulation, i

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2.

Q UES TION:

What is the basis of the time of ten minutes used for operator ac tion ?

What is the maximum time allowed before the safety valves would open ?

(paragraph 6. 2.1. (4) i page 19)

'l A NSWER :

It is generally assumed that ten minuter is more than sufficient time for an operator to determine plant status and initiate correct protective action following an incident.

l In cases where a specific operator action is required, such as l

the initiation of containment spray or manual initiation of l

relief valves for depressurization, it is generally demonstrated i

that the containment or core would not be in danger during the i

ten minute time frame (c. g.

FSAR Sec tion 6. 2. 4. 3).

In regard to the situation referenced, i. e. feedwater line break accompanied by MSIV isolation, there is never any danger to the reactor core.

The level decrease, due to void collapse, would initiate HPCI and RCIC when reactor low water level trip is reached.

Either of these systems can supply sufficient coolant to maintain the 1

reactor water level above the active core.

Operator action is only required in the event that neither of the systems is available.

Thus, if it is assumed that water from the feed-water line spills from the main steam chase to the HPCI compartment, it can be shown that the critical time constraint relative to the ten minute assumption is determined from the rate of flooding in the HPCI compartment.

The time required for the level to reach a critical HPCI component and possibly I

disable the HPCI has been shown to be in excess of ten minutes.

Therefore, the maximum time available for safety / relief valve initiation is some time greater than ten minutes.

The actual point has not been specifically determined since if the HPCI i

operated for ten minutes, the reactor should already be de-pressurized.

Following depressurization of the reactor to 150 psig, the LPCI system will automatically operate to com-plete the plant shutdown.

I

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UlJ1:STION:

Solstoit details ed t ho'.uld i t ion.i l p r otec t ion mentioned in paragraph 6. 2. J(1).

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The additional protection envisioned at the time ANSWER:

l j

of the report was a plate protecting the turbine building mezzanine floor (elevation 931'0") from a jet of water im-j pinging on the floor.

This would also have provided pipe j

whip protection.

Further analysis of the break and break locations resulted in the f ollowing:

i a.

Jet Impingement i

The original calculations assumed that th,e maximum 1

operating pre r.sure of the pump. continued for a long l

period of time.

This was a conservative approach that did not take into account the effects of pump discharge

]

head versus the flow characteristics (system resistance).

l If we ta ke into account these effects (pump run-out), the forces due to jet impingement will be reduced by approx-j imately one order of magnitude.

.Using these new forces l

same method of calculation described in paragraph and the 5.1 of the report, the mezzanine floor will withstand the jet impingement, the reby supporting the redundant safe-guard MCC without adding any steel plate, b.

Pipe Whip In order to provide protection to the mezzanine floor l

against pipe whip, four restraints will be added.

De tail drawings of the pipe restraints are attached.

The design load for the pipe restraint was 161 kips.

t W ith the addition ol' the tour pipe restraints, the mezza-nine floor wil, be protected; thereby insuring safe shutdown of the plant following a feedwater line break.

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4.

_ QUESTION:

Since the torus is not strictly a pipe, the j

statement that the torus will not be damaged because the torus wall thicknes s is greater than that of the HPCI steam i

li ne, may not be accurate. Similar circumstances on other i

BWR torus plants necessitated the installation of impact j

plate s or restraints to prevent the HPCI and RWCU lines from impacting the torus. An analysis must be performed

l to show the impact energy the HPCI line will have on the torus. Please submit such an analysis for all high energy i

lines which could impact the torus (page 23).

i ANSWER:

The only high energy line that may impact the torus is the HPCI primary steam line. The statement con-tained in the report was based on the meeting held in Bethesda, Maryland on February 5,1973 where the same j

point was discus sed.

In performing additional analysis the suppression chamber 1

integrity will be maintained but some permanent deformation of the shell may occur due to pipe whip from postulated break points (see criteria in Appendix A of the report). This shell deformation would not impair the ability of plant personnel to safely shutdown the plant.

We are continuing our analysis and design in order to protect the suppression chamberand present any shell deformation.

i Any restraints required will be installed when the analysis i

and design are completed.

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1 5.

QUESTION:

What are the environmental consequences of a primary steam sample line break on any safety related l

equipment and cabling?

(page 30) l ANSWER: The primary steam sample line is located on the west side of the turbine building.

The line goes from the main steam line (PS I-18-ED) to the sample rack located at j

clevation 937'of the west side of the turbine building.

The west side of the turbine building does not contain any safety related equipment or cabling that would be affected by this break.

Our analysis indicated that a break in this

!" steam sample line would not interfere in the safe shutdown of the plant.

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6.

QUCSh0N:

What are the environmental consequences of a j

main stean. or feedwate r sensing line break on safety related i

equipment or cabling?

(page 32) 1

)

ANSWER:

The main steam instrument sensing lines are routed from the primary steam lines to panel C210 located l

at elevation 951' of the east end of the turbine building, j

Until the lines penetrate the turbine operating deck, they are within the condeser compartment.

There is no safety related i

equipment (except one of two emergency service water lines) i or cabling located within the condenser compartment.

The emergency service water line is a 3" schedule 160 pipe which will not be damaged by the instrument sensing line (l") break per the criteria contained in Appendix A of the re por t.

An instrument sensing line break above the turbine ope rating deck at the rack itself will have negligible environmental consequences.

The safeguard MCC's are located at elevation 91l' and 931' of the east end of the turbine building.

Reactor protection system instrumentation (Turbino/Generatur Load Rejection instruments) located in the general area will not be affected since the cables from these instruments are within conduits and the cabling rated at 90 C.

This rise in air temperature and humidity within the large volume (above the turbine operating deck) due to a a,ensing line break will be minimal.

The break will be detected by an area radiation I

monitor which is located about ten feet from the instrument rack.

l The feedwater instrument sensing lines are located on the east side of the turbine building at ele vation 911'-0".

A break in the feedwater instrument sensing line may possibly affect one of two safeguard MCC's (located at ele vation 911').

This will not interfere with the safe shutdown of the plant following the logic described in the section on feedwater line breaks.

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